Molecular Characterization of the Cytidine Monophosphate-N-Acetylneuraminic Acid Hydroxylase (CMAH) Gene Associated with the Feline AB Blood Group System

Cat’s AB blood group system (blood types A, B, and AB) is of major importance in feline transfusion medicine. Type A and type B antigens are Neu5Gc and Neu5Ac, respectively, and the enzyme CMAH participating in the synthesis of Neu5Gc from Neu5Ac is associated with this cat blood group system. Rare type AB erythrocytes express both Neu5Gc and Neu5Ac. Cat serum contains naturally occurring antibodies against antigens occurring in the other blood types. To understand the molecular genetic basis of this blood group system, we investigated the distribution of AB blood group antigens, CMAH gene structure, mutation, diplotypes, and haplotypes of the cat CMAH genes. Blood-typing revealed that 734 of the cats analyzed type A (95.1%), 38 cats were type B (4.9%), and none were type AB. A family of three Ragdoll cats including two type AB cats and one type A was also used in this study. CMAH sequence analyses showed that the CMAH protein was generated from two mRNA isoforms differing in exon 1. Analyses of the nucleotide sequences of the 16 exons including the coding region of CMAH examined in the 34 type B cats and in the family of type AB cats carried the CMAH variants, and revealed multiple novel diplotypes comprising several polymorphisms. Haplotype inference, which was focused on non-synonymous SNPs revealed that eight haplotypes carried one to four mutations in CMAH, and all cats with type B (n = 34) and AB (n = 2) blood carried two alleles derived from the mutated CMAH gene. These results suggested that double haploids selected from multiple recessive alleles in the cat CMAH loci were highly associated with the expression of the Neu5Ac on erythrocyte membrane in types B and AB of the feline AB blood group system.

Neural stem cell transplantation at critical period improves learning and memory through restoring synaptic impairment in Alzheimer's disease mouse model

Alzheimer's disease (AD) is characterized by neuronal loss in several regions of the brain. Recent studies have suggested that stem cell transplantation could serve as a potential therapeutic strategy to halt or ameliorate the inexorable disease progression. However, the optimal stage of the disease for stem cell transplantation to have a therapeutic effect has yet to be determined. Here, we demonstrated that transplantation of neural stem cells into 12-month-old Tg2576 brains markedly improved both cognitive impairments and neuropathological features by reducing β-amyloid processing and upregulating clearance of β-amyloid, secretion of anti-inflammatory cytokines, endogenous neurogenesis, as well as synapse formation. In contrast, the stem cell transplantation did not recover cognitive dysfunction and β-amyloid neuropathology in Tg2576 mice aged 15 months when the memory loss is manifest. Overall, this study underscores that stem cell therapy at optimal time frame is crucial to obtain maximal therapeutic effects that can restore functional deficits or stop the progression of AD.

Modified lateral orbitotomy for intact removal of orbital dumbbell dermoid cyst

: We describe a modified lateral orbitotomy for intact removal of a dumbbell dermoid cyst involving the frontozygomatic suture. The clinical features and surgical treatment of the case are discussed.

Protective effect of glutathione in HIV-1 lytic peptide 1-induced cell death in human neuronal cells

To elucidate the pathogenic mechanisms involved in neurodegeneration in AIDS patients with cognitive deficits, we have examined the toxic effect of the lentivirus lytic peptide 1 (LLP-1) corresponding to the carboxyl terminus of HIV-1 transmembrane glycoprotein gp41 on human neuronal and glial cell lines. LLP-1 induced a significant lactate dehydrogenase (LDH, a marker of cell death) release from these cells in a concentration- and time-dependent manner, while the noncytolytic LLP-1 analog 2 had little effect. Application of LLP-1 to SH-SY5Y, a well-characterized human neuronal cell line, caused the decline of intracellular glutathione (GSH) content that appeared to occur before a significant LDH release. Furthermore, LLP-1 elicited a significant loss of mitochondrial function as measured by mitochondrial transmembrane potential (MTP). Among the reducing agents and antioxidants tested, GSH and a GSH prodrug N-acetylcysteine (NAC) provided protection against LLP-1-induced neuronal cell death, evidently by restoring the intracellular GSH levels and blocking the disruption of mitochondrial integrity. Thus, gp41-derived LLP-1 may be a potential neurotoxic agent capable of causing the intracellular GSH depletion and disturbing the mitochondrial function, possibly contributing to the neurodegenerative cascade as seen in HIV-1-associated dementia. Our data indicate that restoring both GSH concentration and mitochondrial function may hold promise as possible therapeutic strategies for slowing disease progression of dementia in AIDS patients.

Effects of the beta-amyloid and carboxyl-terminal fragment of Alzheimer's amyloid precursor protein on the production of the tumor necrosis factor-alpha and matrix metalloproteinase-9 by human monocytic THP-1

To explore the direct role of beta-amyloid (Abeta) and carboxyl-terminal fragments of amyloid precursor protein in the inflammatory processes possibly linked to neurodegeneration associated with Alzheimer's disease, the effects of the 105-amino acid carboxyl-terminal fragment (CT(105)) of amyloid precursor protein on the production of tumor necrosis factor-alpha (TNF-alpha) and matrix metalloproteinase-9 (MMP-9) were examined in a human monocytic THP-1 cell line and compared with that of Abeta. CT(105) elicited a marked increase in TNF-alpha and MMP-9 production in the presence of interferon-gamma in a dose- and time-dependent manner. Similar patterns were obtained with Abeta despite its low magnitude of induction. Autocrine TNF-alpha is likely to be a main mediator of the induction of MMP-9 because the neutralizing antibody to TNF-alpha inhibits MMP-9 production. Genistein, a specific inhibitor of tyrosine kinase, dramatically diminished both TNF-alpha secretion and subsequent MMP-9 release in response to CT(105) or Abeta. Furthermore, PD98059 and SB202190, specific inhibitors of ERK or p38 MAPK respectively, efficiently suppressed CT(105)-induced effects whereas only PD98059 was effective at reducing Abeta-induced effects. Our results suggest that CT(105) in combination with interferon-gamma might serve as a more potent activator than Abeta in triggering inflammatory processes and that both tyrosine kinase and MAPK signaling pathways may represent potential therapeutic targets for the control of Alzheimer's disease progression.

Optimal concentration of human epidermal growth factor (hEGF) for epithelial healing in experimental corneal alkali wounds

PURPOSE

By using both in vivo and in vitro (organ-cultured) systems, the optimal concentrations of hEGF to enhance epithelial healing after alkali wounds were evaluated in the rabbit cornea.

METHODS

Alkali-injured corneas (pi = 5.5 mm, 1 N NaOH, 60 s) were treated with 0.01, 0.1, 1.0, 10 and 100 ng/ml hEGF for the in vitro study. The healing of epithelium and endothelium was determined at 1, 2, 3, 4, and 6 days after treatment. For the in vivo experiment, the eyes were treated with 2, 5, 10, and 50 microg/ml hEGF 3 times per day. The measurement of epithelial healing rate, transmission electron microscopy and immunohistochemical observation were performed after 7 days treatment.

RESULTS

In in vitro tests, hEGF enhanced the epithelial healing rates, showing a maximum enhancement at the concentration of 1.0 ng/ml, and endothelial healing was increased at 100 ng/ml. In in vivo studies, no significant difference was observed in the rates of epithelial healing between control and each hEGF-treated group. Among the tested concentrations, 5 microg/ml hEGF induced the most active proliferation of basal cells and 50 microg/ml hEGF remarkably produced a vascular ingrowth to the central wound area. The thickness of re-surfaced epithelium was increased by hEGF in a concentration-dependent manner.

CONCLUSIONS

The results of the present study indicate that a low concentration of hEGF may selectively enhance epithelial healing without affecting endothelial healing. The optimal concentration of hEGF for the stimulation of epithelial healing appears to be 5 microg/ml in rabbit corneal alkali wounds.

Expression of complement inhibitor protein CD59 in human neuronal and glial cell lines treated with HIV-1 gp41 peptides

In attempts to elucidate the pathogenic mechanisms involved in neurodegeneration in AIDS patients with cognitive deficits, the possible effect of HIV-1 transmembrane envelope protein gp41 on expression of the membrane inhibitor of complement mediated cytolysis (CD59) was assessed in human neuronal (SK-N-SH) and astroglial (T98G) cell lines. Western blotting analyses demonstrated that an immunodominant (ID, aa 598-613) gp41 peptide as well as the recombinant gp41 protein encompassing this domain markedly reduced CD59 level in a dose dependent manner whereas p24 and control peptide had little effect. RT-PCR showed that ID peptide also elicited a reduction in the expressed CD59 mRNA level. This gp41 peptide apparently down-regulated phorbol 12,13-dibutyrate induced elevation of CD59 at the protein and mRNA levels in a manner similar to that conferred by protein kinase C inhibitor, H-7 or staurosporine in SK-N-SH. Interestingly, proinflammatory cytokines such as IL-1beta or IFN-gamma as well as LPS greatly decreased CD59 in SK-N-SH and to a lesser extent in T98G whereas TNF-alpha did not significantly alter it. In contrast, antioxidants and anti-inflammatory agents enhanced CD59 expression reversing gp41 peptide mediated inhibitory effect in SK-N-SH. Our data suggest that high level of gp41 or its metabolites as well as impaired protein kinase response, chronic inflammation or antioxidant depletion within HIV-1 infected brains may be associated with a diminished expression of CD59 which would render neuronal cells to susceptible to indirect bystander lysis in the presence of autologous complement.

Effect of HIV-1 gp41 peptides on secretion of beta-amyloid precursor protein in human astroglial cell line, T98G

To understand the mechanism underlying cognitive deficits in AIDS patients, we examined the influence of gp41 peptides on the expression and the secretion of Alzheimer's amyloid precursor protein (APP) in human astroglial cell line T98G. Western blotting analyses demonstrated that treatment of glial cells with a putative immunosuppressive domain (aa 583-599) of gp41 remarkably downregulated the interleukin 1beta- (IL-1beta) induced elevation of the secreted form of APP (sAPP alpha) containing Kunitz-type protease inhibitor (KPI) domain without significant changes of the expression pattern of APP mRNAs as revealed by reverse transcriptase polymerase chain reaction (RT-PCR) analysis. Recombinant gp41 protein encoding for ectodomain, including aa 583-599 residues, also elicited a similar dose-dependent inhibitory effect, whereas the control peptides resulted in little change. The molecular mechanism underlying this gp41-mediated reduction of sAPP alpha secretion appears not to be owing to the difference in the function of extracellular proteases based on the finding of similar proteolytic activities responsible for APP metabolism in vitro present in the conditioned media from the cultures treated with or without gp41 peptide. However, the known PKC inhibitors such as H-7 or staurosporine, partially inhibited the elevation of sAPP alpha secretion in response to protein kinase C (PKC) agonist phorbol 12,13-dibutyrate (PdBu) as well as to IL-1beta, mimicking the immunosuppressive gp41 peptide. These observations implicate that part of the neurodegenerative cascade in AIDS brains may involve the inhibitory effect of gp41 on secretion of sAPP alpha, a potent glial neurotrophic factor, through impaired PKC response.

Increased activity of matrix metalloproteinase-2 in human glial and neuronal cell lines treated with HIV-1 gp41 peptides

Part of the neurodegenerative cascade in AIDS dementia may involve overexpression of matrix metalloproteinases (MMPs). Here, we examined the possible effect of HIV-1 gp41, which has been shown as a key determinant associated with pathogenesis of AIDS dementia, on the activity of MMPs using human neuronal and glial cell lines. Zymographic analysis revealed that treatment with the gp41 peptide (aa 583-599) for 24 h markedly elevated the activity of MMP with Mr 66 kDa in the cultured media of glioblastoma cell line T98G in a concentration-dependent manner as well as of neuroblastoma cell line SK-N-SH despite of lower magnitude of the activity. In contrast, the immediately adjacent gp41 peptide (aa 598-613) as well as the reverse peptide (aa 598-583) had a little effect. Recombinant gp41 protein containing extracellular domain also elicited a similar effect, although with a lesser extent. This 66 kDa MMP was confirmed as gelatinase A (MMP-2) based on the results of its activity dependent on Ca2+ and inhibited in the presence of 1,10-phenanthroline or EDTA, as well as its specific immunoreactivity on the Western blot. N-acetyl cysteine (NAC) downregulated this gp41 peptide-induced MMP-2 activity in T98G. The soluble form of amyloid precursor protein (sAPP), which is synthesized in the Escherichia coli system, also inhibited the MMP-2 activity in vitro. Taken together, these results implicate that high production of HIV-1 gp41 or its metabolites containing aa 583-599 within central nervous system (CNS) could result in the increased activity of MMP-2 and that the extracellular deficiency of reducing agent or decreased level of sAPP within CNS could exacerbate this gp41-induced MMP-2 activity.

Expression of Alzheimer's amyloid precursor protein in human lymphocyte

Beta-amyloid precursor protein (betaAPP) has been shown to be involved in cell growth regulation. In spleen, the majority of cells showing betaAPP like immunoreactivity was found in the T cell-dependent zone. In Northern blot, the expression of betaAPP was increased to reach the peak at 72 h after the treatment of phytohemagglutinin (PHA). But, in cytofluorometry, almost all CD4(+) T helper/inducer cells and the majority of CD(8+) T suppressor/cytotoxic cells show betaAPP immunoreactivity which remained constant during the stimulation with PHA. These results suggest that betaAPP is a surface molecule of T lymphocyte and the turnover or release of APP might be increased with the treatment of T cell mitogen.

Amyloidogenic processing of Alzheimer's amyloid precursor protein in vitro and its modulation by metal ions and tacrine

Recent studies implicate that excessive amyloidogenic pathway of amyloid precursor protein (APP) processing may be the final common pathway involved in the pathogensis of AD. In attempts to identify the proteases or factors leading to excessive amyloid deposition, we evaluated the potential role of acethylcholinesterase (AChE) and its associated protease for amyloidogenic processing of APP in vitro. Prolonged incubation of a recombinant APP770 with AChE produced several amyloidogenic fragments accumulating a relatively stable a 18 kDa A beta (amyloid beta-protein) bearing carboxy terminal peptide, which was further degraded by an increased concentration of AChE. Protease inhibitory profiles confirmed the trypsin-like serine protease activity present in AChE preparation. This observed APP processing was significantly enhanced by Ca2+, Mg2+, or Mn2+ at 1 mM concentration and modulated in concentration dependent manners by metal ions such as Ca2+, Zn2+, Fe2+/Fe3+, Al3+, or a tacrine, a centrally active cholinesterase inhibitor. Our data imply that AChE and its associated protease may be involved in the generation a 18 kDa amyloidogenic peptide under certain physiological condition in vivo and that the gradual changes in their proteolytic activities or locations and the locally disturbed metal homeostasis could be factors associated with abnormal accumulation of APP, eventually leading to amyloid deposition in AD brain. In addition, zinc or tacrine treatment of AD patients with high dosage or in the long term may have effects on the process of amyloidogensis.

Molecular physiology, biochemistry, and pharmacology of Alzheimer's amyloid precursor protein (APP)

The function of APP is not yet known in detail but growing evidence exists that APP may mediate cell interactions with the cell surface or soluble glycoproteins and defense mechanisms in the CNS involving the immune system. We describe here the finding that almost all CD4+ lymphocytes and the majority of CD8+ lymphocytes were positive for A beta and the antibodies against A beta or APP did not inhibit the [3H]-thymidine uptake of mitogen-treated lymphocytes significantly. There were no differences in the A beta immunoreactivity on the cell surface of lymphocytes between Alzheimer's disease (AD) and control samples. Excessive amyloidogenic pathway of APP processing may be the final common pathway involved in the pathogenesis of AD. Thus, the identification of proteases or factors leading to aberrant proteolysis which process APP to yield a variety of potentially amyloidogenic fragments would promise pharmacological targets to develop anti-AD drugs. In attempts to define the proteases or factors which alter the balance between nonamyloidogenic and amyloidogenic processing pathways, our study indicates that thrombin or acetylcholinesterase(AChE)-associated protease may be involved in the amyloidogenic processing pathway of APP in vivo to generate amyloidogenic intermediates linked to amyloid deposition. Highly specific and dose-dependent direct modulation of APP processing by biologically available metal ions including Ca2+, Zn2+, Fe2+/Fe3+ and Al3+ suggest the disrupted metal homeostasis as factors leading to overaccumulation of APP and subsequent aberrant proteolysis utilizing excessive amyloidogenic processing pathway. There is mounting evidence that at least some of the neurotoxicity associated with AD is due to fragments from APP. Most research has focused on the toxic effect and the ion channel activity of A beta in causation of the disease. The possible role of other cleaved products of APP is less clear. We investigated the channel-forming ability of various products of APP when applied to Xenopus oocytes and their neurotoxicity in vitro. CT105 peptide was found to be exceedingly potent at 500 nM concentration in forming nonselective ion channels during application from either outside or inside the oocyte and more toxic than either of the A beta fragments, A beta 25-35, or A beta 1-40. Taken together, these results suggest the possible involvement of CT peptide in inducing the neurotoxicity characteristic of AD through the direct damage on the cell membrane. Therefore, we hypothesize that amyloidogenic CT may make nonselective ion channels or pores in the membrane and may cause neuronal death in the early stage of AD and then further metabolized to more stable and less toxic A beta which may be finally deposited in the brain where it could inflict further toxicity to neurons. Here we report successful inhibition of APP gene expression by antisense oligodeoxynucleotides at the mRNA or the protein level in in vitro and cell culture systems.

Membrane currents induced in Xenopus oocytes by the C-terminal fragment of the beta-amyloid precursor protein

There is mounting evidence that at least some of the neurotoxicity associated with Alzheimer's disease (AD) is due to proteolytic fragments of the beta-amyloid precursor protein (beta APP). Most research has focused on the amyloid beta protein (A beta), which has been shown to possess ion channel activity. However, the possible role of other cleaved products of the beta APP is less clear. We have investigated the ability of various products of beta APP to induce membrane ion currents by applying them to Xenopus oocytes, a model system used extensively for investigating electrophysiological aspects of cellular, including neuronal, signalling. We focussed on the 105-amino-acid C-terminal fragment (CT105) (containing the full sequence A beta), which has previously been found to be toxic to cells, although little is known about its mode of action. We have found that CT105 is exceedingly potent, with a threshold concentration of 100-200 nM, in inducing nonselective ion currents when applied from either outside or inside the oocyte and is more effective than either beta APP or the A beta fragments, beta 25-35 or beta 1-40. The ion channel activity of CT105 was concentration dependent and blocked by a monoclonal antibody to A beta. These results suggest the possible involvement of CT105 in inducing the neural toxicity characteristic of AD.

Age-related changes of mRNA expression of amyloid precursor protein in the brain of senescence-accelerated mouse

APP695 mRNA is only expressed in the brains of SAM. The expression of APP mRNA in SAM P1 mice brains is more marked than that in SAM R1 mice brain. APP mRNA expression was increased with advancing age in all brain regions of SAM P1 mice compared with SAM R1. Especially, the changes of the amount of APP mRNA in the prosencephalon and the mesencephalon are significant at P value of 0.05. We suggest that overexpression of APP mRNA may be related to accelerated aging phenomenon in the SAM brain. This is the first report of age-related increase in the amount of APP mRNA in the SAM brain.

Aggregation of amyloid precursor proteins by aluminum in vitro

The effect of various metal ions on aggregation of human recombinant amyloid precursor protein (APP) in vitro was investigated based on characterizations of altered migration on SDS-PAGE or immunoblots. Most biological metal ions tested had no significant effect on aggregation of APP. In contrast, AlCl3 in particular promoted aggregation of APP or APP-CT105 in a dose dependent manner. This effect of AlCl3 on APP mobility shift was prevented or reversed by the metal chelator, EDTA. Amorphous aggregates were observed in AlCl3 treated APP when examined by EM. These results suggest that aluminum may play a role in the pathogenesis of AD by directly promoting aggregation of APP.

Complete nucleotide sequence and tissue-specific expression of the rat phenylethanolamine N-methyltransferase gene

The rat phenylethanolamine N-methyltransferase (PNMT) gene was isolated from a genomic library by cross-hybridization with a bovine PNMT cDNA probe. Complete nucleotide sequence analysis of a genomic clone showed that this gene contained three exons and spanned about 2.8 kb in length. There were the acute-phase response element, TATA, SP1, and GRE sequences. The physicochemical properties of rat adrenal PNMT were different from those of the brainstem PNMT. However, northern blot and reverse transcription-polymerase chain reaction analysis showed that the rat PNMT gene may not express the multiple forms of mRNA. These results suggest that the rat PNMT gene might produce a single enzyme protein, whose activity may be differentially modulated by tissue-specific environment in the central and peripheral systems.

Overexpression and simple purification of human immunodeficiency virus-1 gag epitope derived from a recombinant antigen in E. coli and its use in ELISA

To develop a test for diagnosis of human immunodeficiency virus-1 (HIV-1) exposure sensitivity, a part of the gag gene was cloned and expressed in Escherichia coli, using expression vectors containing a trp promoter. The immunoreactivity of recombinant protein was determined using HIV-1 specific antibodies in a Western blot analysis. The recombinant plasmid, pYHCgag3, gag gene was fused to the trpE' gene linked to the hydroxylamine (HA) cleavage recognition sequence which was induced to overexpress a core antigen (gag a.a. 121-398 from plasmid BH10) as fusion protein in the form of insoluble inclusion body. Recombinant gag was purified by a simple single step purification procedure. After partial purification of inclusion bodies and subject to the HA-cleavage treatment, gag protein was further purified to homogeneity using DEAE-Sepharose chromatography. The purified core antigen offered reliable results with high sensitivity and specificity for identification of HIV-1 antibodies when tested in the enzyme-linked immunosorbent assay (ELISA). These results suggest that mass production of recombinant core antigen will provide a valuable resource to HIV-1 serodiagnostics for the screening of large groups of blood donors to prevent HIV-1 infection.

Enhancement of EIAV replication and disease by immunization with a baculovirus-expressed recombinant envelope surface glycoprotein

The potential for antibody-dependent enhancement of replication of macrophage/monocyte tropic viruses has posed a significant problem in the development of vaccines for several animal and human viruses and has raised significant concern in the design of potential AIDS vaccines. Using the previously described equine infectious anemia virus/Shetland pony system as a model for HIV-1 vaccine development, we have evaluated the efficacy of a recombinant subunit vaccine containing a baculovirus-expressed envelope surface glycoprotein (gp90) of EIAV. The results of these trials demonstrate not only that the recombinant vaccine failed to protect against infection by standard homologous and heterologous EIAV challenge strains, but that it resulted in a marked enhancement of virus replication and exacerbation of disease in immunized ponies exposed to the heterologous virus strain. Thus, the recombinant EIAV gp90 vaccine provides a novel in vivo model for examining in detail the mechanisms of immune enhancement of a lentivirus infection and for evaluating strategies to avoid the production of deleterious immune responses in AIDS vaccine design.

Bacterial expression, purification of full length and carboxyl terminal fragment of Alzheimer amyloid precursor protein and their proteolytic processing by thrombin

Human amyloid protein precursor(APP770) and its carboxyl terminal portion (CT105) including beta/A4 domain were highly expressed using strong expression systems in E. coli. These recombinant APP peptides were purified with a combination of urea solubilization and ion-exchange chromatography and used for proteolytic processing by thrombin. Three thrombin cleavage sites were predicted by the decrease of APP770 and the appearance of M(r) 56, 27 and 18 kDa fragments containing beta/A4 domain on SDS-PAGE gel and on the immunoblot. A similar but limited proteolysis of platelet APPs exposed to thrombin resulted in the stimulated production of 60 and 27 KDa carboxyl terminal peptides containing the intact beta/A4. This thrombin mediated proteolysis was completely blocked by hirudin, the specific thrombin inhibitor. These results suggest that thrombin may play a role in altered processing of APP to generate potentially amyloidogenic intermediates in vivo leading to amyloid deposition.

Effect of loading and syringing on void formation in automixed addition silicone elastomers

The effect of loading and syringing on void formation in five automixed addition silicones was evaluated by determining the voids created in the first and second halves of material loaded and dispensed from a metal syringe. Impressions were made of a model with six stainless-steel cylinders. The voids were counted at a predetermined site on 3 separate days using a binocular microscope at x 7 magnification. Automixed addition silicones did not confirm the 'last out-fewer bubbles' phenomenon and specific loading and syringing technique did not appear to have a consistent effect on void formation in automixed elastomers.

Breakfast practices in the Asian region

Studies on changing dietary patterns throughout the Asian region have focused largely on overall alterations in nutrient intakes and changes in the consumption of various food groups. Changes in individual meal patterns have received little attention. Although country and regional differences occur, the first meal of the day, breakfast, tends to take the form of a traditional meal in most south-east Asian countries. Grain and cereal products, such as rice and wheat and rice noodles, appear to be dietary staples at breakfast In some countries, the more traditional grain products are being replaced by alternative cereals, such as bread. Lifestyle changes and accompanying urbanization together with rising affluence, appear to be largely responsible for dietary alterations. The health implications of these changes require further investigation.

Single discolored tooth: an alternative treatment approach

A single discolored tooth is often difficult to treat, but one with an obliterated pulp chamber and root canal presents an even greater challenge. The use of nightguard bleaching is offered as a simpler, alternative treatment to either root canal therapy or the removal of sound tooth structure for fabrication of a facial veneer or a complete-coverage crown.

Radiation dosage of a dental imaging system

This study compared the radiation dosage necessary for obtaining clinically acceptable images with a new dental imaging system (radiovisiography) to that required with a conventional-film radiographic technique. Results showed that radiovisiography required significantly less radiation exposure, only 22.3% of that used in the conventional technique. Problems, such as lack of flexibility and the limited size of the x-ray-sensitive surface, are associated with radiovisiography; however, the system effectively complements conventional-film radiography.

Rapid and simple purification of human immunodeficiency virus 1 epitope gp41

In order to develop a reliable and inexpensive serodiagnostic method, part of the transmembrane glycoprotein gene of HIV-1, gp41', (HIV-env 548-646) was cloned into an expression vector, pCT10 with a sequence encoding a hydroxylamine cleavage site and with a part of Lac Z gene (Lac 2": 834 base pairs) as a fusion partner. Overexpression of Lac Z"-gp41' was induced in E. coli and the gp41' fusion protein was purified to homogeneity by centrifugation, hydroxylamine cleavage and an ion-exchange chromatography. Western blot analysis and enzyme-linked immunosorbant assay (ELISA) using the purified gp41 fragment showed high sensitivity and specificity of gp41 as an antigen to detect anti HIV-1 antibodies in testing human sera. These results suggest that this simple and rapid purification method is reliable for obtaining a large quantity of purified gp41'.

Variability of two methods of measuring absorbed dose in dental radiography

Thermoluminescence dosimetry (TLD) has been widely used in the monitoring of radiation exposure in healthcare workers operating radiation devices. This study compared the reliability of TLD to an electronic dosimeter. The absorbed dose registered by the TLD chips was found to be higher than that by the electronic dosimeter. Variability was found to be significantly higher and the variance component attributed to the variability of the method of measurement was more than twice as much in TLD when compared to the electronic dosimeter. It is concluded that TLD is a more variable method of measuring absorbed dose than the electronic dosimeter.

Dental prosthetic status and needs of an elderly population living in long-term care facilities in Singapore

This study examined the prosthetic status and needs among an elderly population living in long-term care facilities in Singapore. A total of 488 subjects were randomly selected and 479 of them were examined. The results show that 56.2 percent of selected subjects were edentulous while 43.8 percent had one or more teeth missing. The average number of teeth present among dentate subjects was 7.5. Of the edentulous subjects, 78 percent of them reported not having any dentures, and more than 20 percent of existing dentures were found to be defective and had to be replaced. A higher proportion (94 percent) of dentate subjects who could have benefitted from having partial dentures did not have them. The findings of this study clearly demonstrate high unmet needs for prosthetic care among an institutionalized elderly population.

Effect of operator variability on void formation in impressions made with an automixed addition silicone

This study examined voids produced in impressions of an automixed addition-reaction silicone. Two operators took the impressions using material dispensed from either intra-oral tips or an impression syringe. The material was also hand-mixed for comparison. There were no differences in the number of voids in the automixed material dispensed using the intra-oral tip or impression syringe. Automixing produced substantially fewer voids than hand-mixing. There was a significant difference in the number of voids in the impressions made by the two operators.

Dental state and needs for episodic care of institutionalized elderly in an Asian community

This study examined the dental state of institutionalized elderly and their need for care. An oral examination was carried out on 479 elderly persons living in long-term care facilities with a mean age of 74.9 years. Results showed an overall DMF score of 27.0 and the average number of teeth in dentate subjects was 7.5. A large proportion of teeth (76.6%) was lost through dental caries and the loss increased significantly with age. Consequently, 56.1% of subjects were edentulous, of whom 78.8% were without dentures. Among the conditions that required urgent dental care, majority of subjects needed extractions of residual roots and loose teeth. A lesser proportion required treatment for gross caries (4.8%), periodontal disease (5.0%), suspected tumor (0.2%), as well as alleviation of pain and infection arising from mucosal lesions (4.8%), abscesses (3.3%) and TMJ problems (2.8%). The treatment needs for dentures and episodic care are high among institutionalized elderly and need to be addressed.

Effectiveness of intraoral delivery tips in reducing voids in elastomeric impressions

Voids in impressions made by five automixed addition silicone elastomers with and without intraoral delivery tips were investigated. The number of voids were counted at a predetermined site on 3 days. Hand-mixed impressions of the automixed materials were made for comparison. There was no statistically significant difference in the mean number of voids produced in each automixed silicone dispensed with the use of intraoral delivery tips and the number of voids produced without the use of the tips. However, there were significant differences in the number of voids among different materials. The rank order of the automixed silicone elastomers was fairly consistent, with Express producing the highest and Reprosil the lowest number of voids. Automixed silicone materials should only be prepared by automixing for optimal results.

Defects in automixed addition silicone elastomers prepared by putty-wash impression technique

Voids presenting in impressions of five automixed addition silicone elastomers were investigated. Impressions were prepared with the putty-light body impression technique on stainless-steel cylinders with acrylic spacers. The number of voids was counted at a predetermined site on three separate days using a stereomicroscope at x7 magnification. Impression specimens of a hand-mixed addition silicone, and from hand-mixing of the automixed materials, were made for comparison. Express gave a significantly higher number of voids than other automixed materials, with President Jet having the lowest void count. Automixed materials generally produced impressions with significantly fewer voids than the hand-mixed material. Automixing was effective in reducing void defects in elastomeric impressions.

Effect of interchanging automatic mixing tips on void formation for an automixed addition silicone impression

This study examined the effect of interchanging mixing tips on void formation for impressions of an automixed addition silicone material. The impressions were made of a series of stainless-steel cylinders by two dentists. The voids were counted at a predetermined site with a binocular microscope. The results showed that there were no significant variations in the number of voids in impressions of the automixed addition silicone using the three different mixing tips. However, one dentist made impressions that had substantially less voids for all three mixing tips.

Porosities in five automixed addition silicone elastomers

Five automixed and one hand-mixed addition silicones were evaluated by counting the number of voids produced in impressions made. It was concluded that although automixing produced fewer voids than hand-mixing, certain automixed materials were better than others.

Dietary tocotrienols reduce concentrations of plasma cholesterol, apolipoprotein B, thromboxane B2, and platelet factor 4 in pigs with inherited hyperlipidemias

Normolipemic and genetically hypercholesterolemic pigs of defined lipoprotein genotype were fed a standard diet supplemented with 50 micrograms/g tocotrienol-rich fraction (TRF) isolated from palm oil. Hypercholesterolemic pigs fed the TRF supplement showed a 44% decrease in total serum cholesterol, a 60% decrease in low-density-lipoprotein (LDL)-cholesterol, and significant decreases in levels of apolipoprotein B (26%), thromboxane-B2 (41%), and platelet factor 4 (PF4; 29%). The declines in thromboxane B2 and PF4 suggest that TRF has a marked protective effect on the endothelium and platelet aggregation. The effect of the lipid-lowering diet persisted only in the hypercholesterolemic swine after 8 wk feeding of the control diet. These results support observations from previous studies on lowering plasma cholesterol in animals by tocotrienols, which are naturally occurring compounds in grain and palm oils and may have some effect on lowering plasma cholesterol in humans.

Lowering of serum cholesterol in hypercholesterolemic humans by tocotrienols (palmvitee)

A double-blind, crossover, 8-wk study was conducted to compare effects of the tocotrienol-enriched fraction of palm oil (200 mg palmvitee capsules/day) with those of 300 mg corn oil/d on serum lipids of hypercholesterolemic human subjects (serum cholesterol 6.21-8.02 mmol/L). Concentrations of serum total cholesterol (-15%), LDL cholesterol (-8%), Apo B (-10%), thromboxane (-25%), platelet factor 4 (-16%), and glucose (-12%) decreased significantly only in the 15 subjects given palmvitee during the initial 4 wk. The crossover confirmed these actions of palmvitee. There was a carry over effect of palmvitee. Serum cholesterol concentrations of seven hypercholesterolemic subjects (greater than 7.84 mmol/L) decreased 31% during a 4-wk period in which they were given 200 mg gamma-tocotrienol/d. This indicates that gamma-tocotrienol may be the most potent cholesterol inhibitor in palmvitee capsules. The results of this pilot study are very encouraging.

Effects of palm oil on cardiovascular risk

A major public health concern of affluent nations is the excessive consumption of dietary fats which are now closely linked to coronary heart disease. Against this scenario, the tropical oils and palm oil in particular, have been cast as major villains in the U.S.A., despite the fact that palm oil consumption there is negligible. The unsuspecting public may not realise that the call to avoid palm oil is nothing more than a trade ploy since in recent years palm oil has been very competitive and has gained a major share of the world's edible oils and fats market. Many also lose sight of the fact that, palm oil, like other edible oils and fats, is an important component of the diet. The allegation that palm oil consumption leads to raised blood cholesterol levels and is therefore atherogenic is without scientific foundation. Examination of the chemical and fatty acid composition of palm oil or its liquid fraction should convince most nutritionists that the oil has little cholesterol-raising potential. The rationale for these are: it is considered cholesterol free. its major saturated fatty acid, palmitic acid (16:0) has recently been shown to be neutral in its cholesterolaemic effect, particularly in situations where the LDL receptors have not been down-regulated by dietary means or through a genetic effect. palm oil contains negligible amounts (less than 1.5%) of the hypercholesterolemic saturated fatty acids, namely lauric acid (12:0) and myristic acid (14:0). it has moderately rich amounts of the hypocholesterolaemic, monounsaturated oleic acid (18:1, omega-9) and adequate amounts of linoleic acid. (18:2, omega-6). It contains minor components such as the vitamin E tocotrienols which are not only powerful antioxidants but are also natural inhibitors of cholesterol synthesis. Feeding experiments in various animal species and humans also do not support the allegation that palm oil is atherogenic. On the contrary, palm oil consumption reduces blood cholesterol in comparison with the traditional sources of saturated fats such as coconut oil, dairy and animal fats. In addition, palm oil consumption may raise HDL levels and reduce platelet aggregability. As with all nutrients, there is a need to obtain a balance of different fatty acids found in fats in edible oils and other food sources. There is no single ideal source of fat that answers to the recent American Heart Association's call to reflect a 1:1:1 ratio of saturated, monounsaturated and polyunsaturated fats in relation to the recommended dietary fat intake of 30% of calories or less.(ABSTRACT TRUNCATED AT 400 WORDS)

Analysis of equine humoral immune responses to the transmembrane envelope glycoprotein (gp45) of equine infectious anemia virus

Defined segments of the transmembrane envelope glycoprotein (gp45) of equine infectious anemia virus were expressed as TrpLE fusion proteins and examined for their reactivity in Western immunoblots against a diverse panel of equine immune sera. The most immunogenic region of gp45 was localized to its amino terminus, positioned between the hydrophobic fusion and the transmembrane domains. A series of overlapping synthetic peptides were used in enzyme-linked immunosorbent assays to define an immunodominant epitope within this region. In contrast, the carboxy-terminal half of gp45 displayed both weak and variable immunoreactivity with equine immune sera.

Characterization of the antigenic domains of the major core protein (p26) of equine infectious anemia virus

A panel of recombinant trpLE-gag fusion proteins and synthetic peptides was used in Western immunoblot and enzyme-linked immunosorbent assays to identify segments of the major core protein (p26) of equine infectious anemia virus that are antigenic in horses during experimental and natural infections with the virus. The predominant humoral immune response was directed toward a highly immunogenic domain composed of 83 amino acids from the carboxy terminus of p26. The observed immunogenicity of p26 resembled that reported for p24 of human immunodeficiency virus type 1, suggesting the conservation of structural motifs in the lentiviral core proteins which are responsible for their observed immunogenicity during persistent lentivirus infections.

Relationship of viscosity to porosities in automixed elastomeric impressions

Porosities commonly presenting as voids have been recognized as an inherent problem in elastomeric impressions. Automixing of the impression has been found to be effective in reducing voids. The purpose of this study was to compare formation of voids in medium-viscosity and putty-wash materials in four automixed addition silicone elastomers. Impressions of a master model were made according to manufacturers' recommendations on manipulation of materials. Voids presenting on a predetermined surface were counted under a binocular microscope at a magnification factor of 7x. Results showed that Express exhibited a significantly higher number of voids than other materials in both categories. Putty-wash impressions generated significantly less voids than medium-viscosity impressions for all materials except Reprosil. The findings of this study suggested that putty-wash impressions produced significantly less porosities than medium-viscosity impressions and, consequently, offer better tear strength for impressions.

Determination of an optimal magnification for examining voids in elastomeric impressions

Specimens of one polyether impression material and the resulting stone casts were examined at magnifications from 1X to 10X to determine the optimal magnification for identifying defects. Results showed that the number of defects on impressions and stone dies detected by two operators increased with each corresponding increase in magnification up to magnifications of 9X and 8X, respectively. The magnifications that revealed significantly less defects than the highest mean count were 6X for impression voids and 5X for stone die defects. A magnification of 9X optimized reliability by maximizing void detection while minimizing operator variability.

Relationship between critical convergence angle and surface defects in stone casts

Surface defects on stone casts threaten the accuracy of cast restorations. The aim of this study was to examine the relationship between critical convergence angle and voids in stone casts. Three addition silicone materials, one condensation silicone material, and one polyether impression material were used. The highest convergence angle at which voids presented at the tip of the specimens was recorded, and the number of voids found at margins and line angles of the tooth preparations were counted. Results showed a positive and significant correlation between the critical convergence angle and the number of voids at margins and line angles of stone casts. Casts poured from polyether impressions registered significantly lower critical convergence angle values and presented with fewer voids than did those fabricated from silicone materials.

Relationship between contact angles of die stone on elastomeric impression materials and voids in stone casts

Poor wettability of elastomeric impression materials results in surface defects on stone casts. This study examined the relationship between contact angles of die stone and voids in casts produced from five medium-viscosity impression materials. Contact angles of a die stone material formed against impression specimens made from polyether, addition and condensation silicones were measured by reflex microscope. The contact angle values achieved on the hydrophilic addition silicones were significantly higher than the polyether but lower than other silicone materials. Contact angle values correlated with the number of voids found at margins and line angles of stone casts but not with those on smooth surfaces.

The effect of mixing method on void formation in elastomeric impression materials

This study compared an automixed elastomer with five hand-mixed elastomeric impression materials by counting the number of voids at a predetermined site using 6 X magnification. Although no samples were free of voids, automixing produced substantially fewer voids than hand mixing.

The adverse consequences of heavy Trichuris infection

Sixty-seven children with heavy Trichuris trichiura infection (Group A) were compared to 73 control children of similar socio-economic status but with light or no T. trichiura (Group B), for nutritional status, rates of concomitant bacterial and protozoal, and symptoms and clinical signs associated with heavy T. trichiura infection. Anoscopy was used to determine heavy T. trichiura infection. Measurements and physical examination were done on Group A on admission to and discharge from hospital; 46% were seen on follow-up visit two to eight months later. Children in Group B were seen only once. There were significant differences for nutritional status (p less than 0.01) and rates of bacterial and protozoal co-infection (p less than 0.01) and a significantly greater rate of invasive amoebiasis in Group A. After treatment, nutritional parameters of Group A children improved significantly, symptoms and clinical signs decreased and there was also a significant decrease in the rate of concomitant bacterial and protozoal infection. Subgroups of Group A children, with and without concomitant enteropathogens, revealed that infection with Entamoeba histolytica and bacterial enteropathogens had had no significant impact on clinical and nutritional status.